Realizamos medidas dielétricas a baixas freqüências (10-2-40Hz) em cristais de KCN empregando uma ponte de ultra-baixas freqüências, bem como a altas freqüências (50-104 Hz) empregando uma ponte de capacitância comercial (General Radio). As curvas de perda dielétrica mostraram um bom ajuste entre altas e baixas freqüências. Obtivemos picos de perda dielétrica num intervalo de cinco décadas e entre 53 e 78K. Os picos destas curvas foram ajustados segundo uma equação de Arrhenius, e obtivemos uma energia de ativação de 0,148 eV e um tempo de relaxação característico de 6,53 x 10-15s para os dipolos CN-. Para temperaturas entre 53 e 59K observamos o aparecimento gradual de um segundo pico de perdas de 25Hz. Sua origem ainda não é conhecida, mas isto sugere que o cristal de KCN pode apresentar propriedades de um dielétrico composto, com dois mecanismos de relaxação distintos. / Dielectric measurements were performed at low frequencies (10-2- 40Hz) with an ultra-low frequency bridge in KCN crystals , as well as at high frequencies (50-10-4 Hz) employing a commercial capacitance bridge (General Radio). The dielectric loss curves show a good adjustment between the high and low frequencies. We obtain dielectric loss peaks in a window of five decades and in the range of 53 and 78 K. The peaks of these curves were fitted with an Arrhenius expression giving for the CN- dipoles an activation energy of 0,148eV and an attempt relaxation time of 6,53x10-15. At temperatures between 53 and 59K we observed the gradual appearing of a second loss peak for frequency of 25Hz. Its origin is not yet known butt his suggestt that the KCN, crystal may present compound dielectric properties , with - two distinct relaxation mechanisms.

In this thesis, I report on the investigation of the low frequency vibrational modes in a number of different systems using ultrafast spectroscopic techniques. These consist of biological systems, including the enzyme, morphinone reductase (MR) and the related biomolecules, riboflavin (Rb) and flavin mononucleotide (FMN), as well as non-biological systems, including the semiconductor gallium nitride (GaN) and gold nanoparticles (Au NPs). The term low frequency refers to terahertz (THz) frequencies, where vibrational modes exist at the molecular level, with molecular rotations, lattice vibrations and inter- and intra-molecular vibrations occurring in the THz spectral range. These vibrational modes occur on sub-picosecond timescales and therefore ultrafast techniques utilising femtosecond laser pulses provide a means of studying these modes, and are employed throughout this thesis. The two ultrafast techniques of transient absorption (TA) spectroscopy and terahertz time-domain spectroscopy (THz-TDS) were used. Firstly, a high-repetition rate transient absorption (HRRTA) spectrometer was commissioned to perform pump-probe measurements with an ultraviolet pump and broadband visible probe. The performance of the HRRTA spectrometer was benchmarked using Au NPs and used to investigate the existence of a promoting vibration in MR contributing to the catalysis process, predicted to occur at THz frequencies. Weak oscillations were detected in the charge-transfer absorption band of MR bound to the non-reactive cofactor 1,4,5,6-tetra-hydro-nicotinamide adenine dinucleotide (NADH4), with a frequency of approximately 1.5 THz and provide evidence of the first direct observation of a promoting vibration in an enzyme. To complement the TA measurements, THz-TDS was also used to obtain direct measurements of the absorption at THz frequencies. Due to the challenge of studying water-based biological samples, an initial investigation was performed on a wurtzite GaN wafer, which exhibited optical phonon modes in the THz frequency range that were found to determine the dielectric response of the semi-insulating semiconductor wafer. Use of a non-polar m-plane wafer allowed the anisotropic nature to be observed and values of 9.22 ± 0.02 and 10.32 ± 0.03 for the static dielectric constants were obtained for the THz electric field polarised both perpendicular and parallel to the c-axis of the wurtzite GaN wafer, respectively. Finally, biological studies using THz-TDS were performed with measurements on Rb pellets and films revealing vibrational modes in the THz region. The sharp absorption features were not observed in FMN, despite a small difference in molecular content from Rb, and dehydration was required to reveal small amplitude absorption features. Final measurements on MR and MR-NADH4 films were carried out and evidence of absorption features in the THz frequency range were observed, however further work is required to determine the precise origin of these features.

Landslides are one of the most dangerous geological hazards. In the United States, landslides cause a damage of $ 3.5 billion and kill 25 to 50 people annually. Shallow landslides occurring near any transportation facilities (railways and highways) can cause economic loss and disturbance of services which lead to indirect economic loss. It also increases the maintenance cost of those facilities. Hence, facilities located near a shallow landslide prone area should be monitored so as to avoid any catastrophic damages. Soil moisture and movement of the soil mass are prime indicators of potential shallow slide movements. This assessment of wireless instruments considers a variety of devices ranging from devices for monitoring tilt and moisture at specific points in the soil mass to ground penetrating radar (GPR), which can give indications of moisture accumulation in soils over a wide spatial extent. For this assessment study, a low cost MEMS accelerometer was selected for measuring tilts and motions. And EC type soil moisture sensor was selected to measure soil moisture content of embankments. The instrumentation of railway embankments works effectively and cheaply when a suspected problem area has already been identified and monitoring is needed over a limited spatial extent. This makes the monitoring system highly localized which often fails to cover potentially new failure prone areas. It is not feasible to use this approach to monitor soil conditions along the entire alignment of the railway. Therefore, another approach, GPR, is defined and explained in this study. GPR measures the dielectric constant value for any given material including soils. In soils, the dielectric constant value depends on the volumetric amount of water content present in a soil. Due to moisture infiltration, there is a reduction in suction value on embankment which indicates a decrease in shear strength of slope. Therefore, a correlation between suction and dielectric constant value is formulated in this study using Complex Refractive index model/Time propagation (CRIM/TP) model for soils. To validate this theoretical correlation, a laboratory study was conducted on pure kaolinite and on normal soil. For pure kaolinite this correlation proves beneficial while, for other type of soil, the correlation was off due to the limitations in filter paper test to measure suction below 2.5pF.

Sol-gel process was utilized to produce organic/inorganic composite in this research, and the effect of mixing time¡]of polymer¡¦s and silica¡¦s precursor¡^ and coupling agent were investigated. To get low к materials was also the important objective. TMA, TGA, SEM, FT-IR, and RF impedance were used to investigate thermal properties, chemical bonding, morphology, and dielectric constant, respectively. The experiments showed that mixing time influence little to thermal stability but a lot to morphology and к. When mixing time was nearer to reaction time, the particle of silica was larger and the surface was flatter. The materials with coupling agent didn¡¦t show the same tendency as one without coupling agent. Regardless of coupling agent, it got larger к when mixing time was nearer to reaction time. Comparing with pure polymer, the modified materials got lower к. The lowest к got in this research was 2.36 which was lower than other materials.

In this thesis, the leakage-mechanism after O2-plasma treatments was investigated. And the mechanism is transformed from Schottky emission into ionic conduction due to moisture uptake after porous silica film undergoes O2 plasma ashing. Besides, CMP process can to recover the damaged films by removed the degraded parts. From the result, we know that O2 plasma causing the bulky damage. Finally, the resistance of metal penetration of O2 plasma treated POSG is performed by utilizing BTS test. It was found that the moisture uptake in POSG films assisting metals in ionization process. Then, the penetrated metal ions in POSG film causes the leaky characters degraded.

Abstract As ULSI circuits are scaled down to deep submicron regime, interconnect delay becomes increasingly dominant over intrinsic gate delay. To reduce the RC delay time, many low dielectric constant materials have been developed. One of the most promising low-k materials is siloxane-based hydrogen silsesquioxane (HSQ) having the general formula (HSiO3/2)2n, n=2, 3, etc. available as Flowable Oxide (FOx). But low mechanical strength is the problem of HSQ. In order to modify the material composition and mechanical intensity of HSQ, a novel siloxane-based inorganic spin-on material Modified-HSQ has been developed for intermetal dielectric applications. In this thesis, the Intrinsic Properties of M-HSQ was investigated. And the effect of H2, O2 plasma treatment was investigated. Besides, In order to avoid the damage when remove the PR, to achieve small linewidth and reduce linewidth fluctuations. We employed E-Beam lithography to pattern the M-HSQ film. The leakage current of M-HSQ film by E-Beam curing is lower than film by conventional process.

As integrated circuits (ICs) are scaled down to deep submicron regime, interconnect delay becomes increasingly dominant over intrinsic gate delay. To solve the issue, two realistic methods are accepted popularly. On the one hand we use copper as the conductor for multilevel interconnects to decrease the resistance part of the RC delay. On the other hand we should reduce the coupling capacitance between the metal lines and this requires a low dielectric constant material. However, some difficulties come up in integrating low-k material with copper wires, including dielectric integrity and high diffusivity of copper ions. In order to prevent copper from penetrating into dielectric material under high electric fields and operation temperature, barrier dielectric have been developed to enhance resistance against copper drift. Silicon carbide (SixCy) with lower dielectric constant (k=4~5) is a promising barrier dielectric material to replace typically used silicon nitride (SixNy), (k~8). In this thesis, we will discuss the basic material properties of silicon carbide and the issues which will meet in process integration and actual working such as thermal cycles and operating under an electric field and a high temperature environment simultaneously. We investigated the conduction mechanism of the leakage current and tried to extract the physical parameters among it. In addition, the electrical properties of Silicon carbide at low temperature were also an important part of our research. Finally, we proposed some reasonable models to demonstrate the phenomenon and results we observed.

Realizamos medidas dielétricas a baixas freqüências (10-2-40Hz) em cristais de KCN empregando uma ponte de ultra-baixas freqüências, bem como a altas freqüências (50-104 Hz) empregando uma ponte de capacitância comercial (General Radio). As curvas de perda dielétrica mostraram um bom ajuste entre altas e baixas freqüências. Obtivemos picos de perda dielétrica num intervalo de cinco décadas e entre 53 e 78K. Os picos destas curvas foram ajustados segundo uma equação de Arrhenius, e obtivemos uma energia de ativação de 0,148 eV e um tempo de relaxação característico de 6,53 x 10-15s para os dipolos CN-. Para temperaturas entre 53 e 59K observamos o aparecimento gradual de um segundo pico de perdas de 25Hz. Sua origem ainda não é conhecida, mas isto sugere que o cristal de KCN pode apresentar propriedades de um dielétrico composto, com dois mecanismos de relaxação distintos. / Dielectric measurements were performed at low frequencies (10-2- 40Hz) with an ultra-low frequency bridge in KCN crystals , as well as at high frequencies (50-10-4 Hz) employing a commercial capacitance bridge (General Radio). The dielectric loss curves show a good adjustment between the high and low frequencies. We obtain dielectric loss peaks in a window of five decades and in the range of 53 and 78 K. The peaks of these curves were fitted with an Arrhenius expression giving for the CN- dipoles an activation energy of 0,148eV and an attempt relaxation time of 6,53x10-15. At temperatures between 53 and 59K we observed the gradual appearing of a second loss peak for frequency of 25Hz. Its origin is not yet known butt his suggestt that the KCN, crystal may present compound dielectric properties , with - two distinct relaxation mechanisms.

In this thesis, we capitalize on the two-dimensional (2D) nature of MXenes by using them as precursors for the synthesis of 2D functional material. MXenes are easily intercalated with monovalent cations K, Na, Li due to their expanded d-spacing after etching. Based on these ideas, we have developed new synthesis processes of texture functional materials using MXenes as precursors. We have successfully synthesized two-dimensional Nb2C MXene based high aspect ratio ferroelectric potassium niobate (KNbO3) and well-oriented photoluminescent rare earth doped lithium niobate (LiNbO3:Pr3+) crystals, which have great potential in opto-electronics applications. In addition, this thesis demonstrates that poly(vinylidene fluoride) (PVDF)-based percolative composites using two-dimensional (2D) MXene nanosheets as fillers exhibit significantly enhanced dielectric permittivity. Furthermore, we fabricated MXene/in-plane aligned PVDF photo-thermo-mechanical solar tracking actuator for energy harvesting applications.

The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid solutions have relative high dielectric constant and low dielectric loss. With increasing sintering temperature, the dielectric constant showed the maximum at 1150°C. The leakage current of BMN ceramic material is extraordinary small. When the voltage and thickness of the BMN capacitor are 4000V and 300um, the leakage current amounts only about 0.13-0.65 . The excellent physical and electrical properties make BMN thin films promising for potential tunable capacitor applications.